WO2014/199758A1, for example, discloses one example of conventionally-known tidal current meters. With this tidal current meter, reception waves received by a plurality of transducers are processed by reception signal processors (reception amplifiers, ADCs, filters, and frequency detecting units) provided corresponding to the respective transducers. Further, the tidal current meter calculates a speed of a tidal current based on Doppler shift frequencies detected by the respective reception signal processors.
With the tidal current meter disclosed in WO2014/199758A1, since the reception signal processors are provided corresponding to the respective transducers as described above, the tidal current meter becomes a redundant system as a whole.